This invention relates to IC card systems which perform transactions with a combination of IC cards containing integrated circuits and card terminals.
The recent years have been called the "cashless era," by using cards issued by credit companies, etc., the purchase of goods without any handling of cash has been possible. Up to now, plastic cards, embossed cards, and magnetic stripe cards have generally been used, but these cards are easy to forge, and their misuse has been problematic. To solve this problem, an information card, called IC card has been developed. In this card, an IC circuit is contained in which a personal identification number is stored. Incorporated within this IC circuit is a personal identification number that is not easily read out from the outside. This IC card is advantageous in that it is difficult to duplicate, its secrecy maintenance capability is excellent, and it can store a great amount of data. Since the personal identification number is input directly by the card user, other persons, for example, a bank clerk, cannot find out the personal identification number. In this respect, the card has a very high security factor.
However, if something is wrong with the internal circuit of the IC card which is essential to data exchange between the IC card and the card terminal, an abnormality will occur in the data transfer. Therefore, erroneous data exchange and storage will be made, causing an error in the transaction.